Sidewall stopper for MEMS device

ABSTRACT

The present disclosure relates to a microphone. In some embodiments, the microphone may comprise a substrate, a diaphragm, a backplate, and a sidewall stopper. The substrate has an opening disposed through the substrate. The diaphragm is disposed over the substrate and facing the opening of the substrate. The diaphragm has a venting hole overlying the opening of the substrate. A backplate is disposed over and spaced apart from the diaphragm. A sidewall stopper is disposed along a sidewall of the venting hole of the diaphragm and thus is not limited by a distance between the movable part and the stable part. Also, the sidewall stopper does not alternate the shape of movable part, and thus will less likely introduce crack to the movable part. In some embodiments, the sidewall stopper may be formed like a sidewall stopper by a self-alignment process, such that no extra mask is needed.

REFERENCE TO RELATED APPLICATION

This Application claims the benefit of U.S. Provisional Application No.62/738,077, filed on Sep. 28, 2018, the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND

Microelectromechanical systems (MEMS) devices, such as accelerometers,pressure sensors, and microphones, have found widespread use in manymodern day electronic devices. MEMS devices may have a movable part,that is used to detect a motion, and convert the motion to electricalsignal. For example, MEMS accelerometers and microphones are commonlyfound in automobiles (e.g., in airbag deployment systems), tabletcomputers, or in smart phones. A MEMS accelerometer includes a movablepart that transfers the accelerating movement to an electrical signal. Amicrophone includes a movable membrane that transfers the sound to anelectrical signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a top view of a diaphragm in a MEMS microphone with a sidewallstopper in accordance with some embodiments.

FIG. 2 is a cross-section view showing a MEMS microphone with a sidewallstopper in accordance with some embodiments.

FIG. 3 is a cross-section view of a MEMS microphone with a sidewallstopper in accordance with some alternative embodiments, the MEMSmicrophone having dual composite backplates.

FIGS. 4-15 illustrate a series of cross-sectional views of a MEMSmicrophone that has a diaphragm with a sidewall stopper at variousstages of manufacture in accordance with some embodiments.

FIG. 16 illustrates a flow diagram of a method for manufacturing a MEMSmicrophone in accordance with some embodiments.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Moreover, “first”, “second”, “third”, etc. may be used herein for easeof description to distinguish between different elements of a figure ora series of figures. “first”, “second”, “third”, etc. are not intendedto be descriptive of the corresponding element. Therefore, “a firstdielectric layer” described in connection with a first figure may notnecessarily corresponding to a “first dielectric layer” described inconnection with another figure.

Many micro-electromechanical system (MEMS) devices can be manufacturedusing semiconductor device fabrication methods. For MEMS devices withmovable parts, stoppers are commonly attached on those movable parts, orcorresponding stable or movable parts of the MEMS device that couldpossibly be contacted by the movable parts, such that the MEMS device isprotected from damage, and/or the movable parts are prevented fromstiction to the corresponding stable or movable parts.

One approach to fabricate a stopper for a MEMS device is by integratingprotrusion structures to the stable or movable parts of the MEMS device.For example, forming an extra “tip” or a “protrusion” on the movablemembrane or the corresponding location of the stable part that couldcontact the movable membrane. One problem of this approach is that theMEMS device can crack easily due to the non-flat membrane topographyinduced by the protrusion structures. Increasing thickness of themovable membrane may help to alleviate this issue, but the detectingsensitivity would suffer. Also, a height of the stopper cannot exceed adistance between the movable membrane and the stable part. Thisdimension limitation becomes a more serious issue when a small devicefootprint is needed.

In view of above shortcomings, the present disclosure is directed to aMEMS device including a sidewall stopper, and an associated method offormation. As an example application, the MEMS device can be amicrophone. The microphone includes a substrate having an opening and adiaphragm facing the opening in the substrate. The diaphragm includes atleast one venting hole. A sidewall stopper is disposed along sidewallsof the venting hole of the diaphragm. In some embodiments, an upperportion of the sidewall stopper contacts a top surface of the diaphragm,and an lower portion of the sidewall stopper contacts a bottom surfaceof the diaphragm. The upper portion and the lower portion of thesidewall stopper may clamp the diaphragm therebetween. The sidewallstopper is attached to an edge of a movable part of the MEMS device (forexample, a perimeter edge of the venting hole of the microphone'sdiaphragm), and thus is not limited by a distance between the movablepart and the stable part. Also, the sidewall stopper does not alternatethe shape of movable part, and thus will less likely introduce crack tothe movable part. In some embodiments, the sidewall stopper may beformed like a sidewall stopper by a self-alignment process, such that noextra mask is needed.

FIG. 1 and FIG. 2 show an example of MEMS devices including a MEMSmicrophone 90 fabricated on a substrate 40. As shown in FIG. 2, the MEMSmicrophone 90 includes a backplate 60 and a diaphragm 50 spaced apartfrom the backplate 60. Both the backplate 60 and the diaphragm 50 can beelectrically conductive, which form a capacitive element. An electricalcontact 82 is electrically connected to the backplate 60 and forms afirst terminal for the capacitive element, and an electrical contact 84is electrically connected to the diaphragm 50 and forms a secondterminal for the capacitive element. FIG. 1 is a top view of thediaphragm 50 of the MEMS microphone 90 in FIG. 2. The cross section A-A′of the diaphragm 50 is illustrated in FIG. 2. The diaphragm 50 includesmultiple venting holes 55 distributed on the diaphragm 50 (e.g., ventingholes as shown or a different amount with varied dimensions). Thediaphragm 50 also includes one or more anchor areas 58 located near aboundary of the diaphragm 50. The anchor areas 58 allow the boundary ofthe diaphragm 50 to be fixed relative to the backplate 60 and allow gapsbetween the diaphragm 50 and the backplate 60 to be changed at otherlocations on the diaphragm at some distance away from the anchor areas58, for example, at the center of the diaphragm 50. The diaphragm 50 isdeformable by energy of sound waves to make the diaphragm 50 bendtowards or away from the backplate 60, as the sound waves exertpressures on the diaphragm 50 through an opening 45 in the substrate 40.The backplate 60 has multiple open areas 65. There is an air volumespace 74 between the diaphragm 50 and the backplate 60. Air can get outof or get into the air volume space 74 through the air passages formedby the open areas 65 on the backplate 60 and/or by the venting holes 55on the the diaphragm 50, as the diaphragm 50 bends towards or away fromthe backplate 60. The bending movement of the diaphragm 50 relative tothe backplate 60 caused by the sound waves changes the capacitance ofthe capacitive element between the diaphragm 50 and the backplate 60.Such change of the capacitance can be measured with the electricalcontact 82 and the electrical contact 84.

FIG. 1 is a top view of the diaphragm 50 of the MEMS microphone 90 inFIG. 2. The cross section A-A′ of the diaphragm 50 is illustrated inFIG. 2. The diaphragm 50 includes multiple venting holes 55 distributedon the diaphragm 50 (e.g., venting holes as shown or more). Thediaphragm 50 also includes one or more anchor areas 58 located near aboundary of the diaphragm 50.

As shown by FIG. 1 and FIG. 2, a sidewall stopper 85 is disposed along aperimeter edge and a sidewall of the venting hole 55 of the diaphragm50. In some embodiments, an upper portion of the sidewall stopper 85contacts a top surface of the diaphragm 50, and a lower portion of thesidewall stopper 85 contacts a bottom surface of the diaphragm 50. Theupper portion and the lower portion of the sidewall stopper 85 may clampthe diaphragm 50 therebetween. Thus, the sidewall stopper 85 extendsvertically above and below the diaphragm 50 and thus is not limited by adistance between the diaphragm 50 and the backplate 60. In someembodiments, a vertical height h of the diaphragm 50 may be greater thana distance d between the diaphragm 50 and the backplate 60 when thediaphragm 50 locates at a relax position. A relax position of thediaphragm 50 is a position when the diaphragm 50 is not bended, moved,or deformable due to the energy of sound waves. The sidewall stopper 85prevents stiction between the diaphragm 50 and the backplate 60.

FIG. 3 shows a cross-section view of a MEMS device 95 with a sidewallstopper 85. In some embodiments, the MEMS device 95 comprises asubstrate 40. In some embodiments, the substrate 40 can be amonocrystalline silicon substrate or a semiconductor-on-insulator (SOI)substrate (e.g., silicon on insulator substrate). For example, thesubstrate 40 can be silicon, glass, silicon dioxide, aluminum oxide, ora combination thereof. In some embodiments, CMOS circuit can befabricated on a silicon substrate. The substrate 40 has an opening 45disposed through the substrate 40. A diaphragm 50 is disposed over thesubstrate 40 and faces the opening 45 of the substrate 40. The diaphragm50 has an opening disposed through the diaphragm. A sidewall stopper 85is disposed along an edge perimeter of the opening of the diaphragm. Thesidewall stopper 85 extends upwardly to exceed a top surface 50 t of thediaphragm 50 and extends downwardly to exceed a bottom surface 50 b ofthe diaphragm 50. In some embodiments, the opening of the diaphragm 50is a venting hole 55 with a cylinder shape. The sidewall stopper 85 mayhave a ring shape that continuously extends along a perimeter of theopening of the diaphragm 50. The sidewall stopper 85 may also laterallyextend across an edge of the opening of the diaphragm. Thus an upperportion of the sidewall stopper 85 contacts a top surface of thediaphragm 50 and a lower portion of the sidewall stopper 85 contacts abottom surface of the diaphragm 50. The upper portion and the lowerportion of the sidewall stopper 85 clamp the diaphragm 50 therebetween.In some embodiments, the sidewall stopper 85 comprises silicon nitride.In some alternative embodiments, the sidewall stopper 85 comprisespolysilicon.

In some embodiments, the diaphragm 50 may include multiple venting holeswith the same or different dimensions to balance a first pressure at oneside of the diaphragm 50 (e.g., the side near the opening 45) with asecond pressure at the other side of the diaphragm 50 (e.g., the sidenear the second backplate 60). Such balancing of the two pressures candecrease the chance of breaking the diaphragm 50 when a large airpressure is present at a location near the opening 45 of the diaphragm50. The diaphragm 50 may also include some other openings disposedpartially or through the diaphragm 50. The sidewall stopper disclosedabove may be clamped on the edges of all those varies openings.

In some embodiments, the MEMS device 95 further comprises a firstbackplate 30 disposed between the diaphragm 50 and the substrate 40 andfacing the opening 45 of the substrate 40. The MEMS device 95 mayfurther comprise a second backplate 60 disposed over the diaphragm 50.The diaphragm 50 is spaced apart from the first backplate 30 by a firstdistance d1 and spaced apart from the second backplate 60 by a seconddistance d2. In some embodiments, the diaphragm 50 and the firstbackplate 30 form two conductive terminals of a first capacitiveelement; the diaphragm 50 and the second backplate 60 form twoconductive terminals of a second capacitive element. The first backplate30 and the second backplate 60 may comprise a conductive layer. Thefirst backplate 30 and the second backplate 60 may also respectivelycomprise multiple layers stacked together. For example, the firstbackplate 30 and the second backplate 60 can respectively comprise afirst silicon nitride layer, a second silicon nitride layer and apolysilicon layer disposed between the first silicon nitride layer andthe second silicon nitride layer. An electrical contact 82 iselectrically connected to the second backplate 60 that forms a firstterminal for a capacitive element, and an electrical contact 84electrically connected to the diaphragm 50 that forms a second terminalfor the capacitive element. In addition, the MEMS microphone 95 caninclude one or more contacts (e.g., a contact 86) that connect topre-fabricated CMOS circuits (not shown in the figure) on the substratethrough via holes. The pre-fabricated CMOS circuits can provide theelectronics for supporting the operation of the MEMS microphone 95.

FIGS. 4-15 are cross-sectional views showing a method of manufacturing aMEMS microphone that has a diaphragm with a sidewall stopper inaccordance with some embodiments.

As shown in a cross-sectional view in FIG. 4, a connecting structure 86Aand a dielectric layer may be formed over a substrate 40. In variousembodiments, the substrate 40 can be, for example, silicon, glass,silicon dioxide, aluminium oxide, or the like. The dielectric layer 70Acan be an oxide material (e.g., SiO2). In some embodiments, thedielectric layer 70A can be formed by way of a thermal process. In otherembodiments, the dielectric layer 70A can be formed by a depositionprocess, such as, chemical vapor deposition (CVD), physical vapordeposition (PVD), or atomic layer deposition (ALD). The dielectric layer70A then is patterned according to a masking layer (not shown) to formtrenches or via holes for the connecting structure 86A to be formed. Forexample, a via hole as shown in FIG. 4 can be formed through thedielectric layer 70A. A conductive material may be filled in thetrenches or via holes to form the connecting structure 86A within thedielectric layer 70A.

As shown in a cross-sectional view in FIG. 5, a first backplate 30 isformed on the dielectric layer 70A. In some embodiments, the firstbackplate layer 30 may be formed by depositing a conformal layer ofpoly-silicon with a suitable deposition technique, such as physicalvapor deposition (PVD) or chemical vapor deposition (CVD). In some otherembodiments, the first backplate layer 30 includes three layers whichare formed by first depositing a layer of silicon nitride 30A, continuedby depositing a layer of poly-silicon 30B, and followed by depositinganother layer of silicon nitride 30C. Each of these three layers can beformed with PVD, CVD, or any other suitable techniques. After thedeposition, the first backplate layer 30 is patterned according to amasking layer (not shown) to form a first backplate 30 includingmultiple open areas 35.

As shown in a cross-sectional view in FIG. 6, a diaphragm layer 100 isformed over the first backplate 30 and spaced apart from the firstbackplate 30 by a first interlayer dielectric layer 70B. In someembodiments, the first interlayer dielectric layer 70B is an oxide layerand is deposited over the first backplate 30 and the dielectric layer70A followed by a planarization process. The diaphragm layer 100 may bedeposited on top of the first interlayer dielectric layer 70B with asuitable technique, such as chemical vapor deposition (CVD), followed bya first patterning process. The first patterning process may beperformed to etch the diaphragm layer 100 to discrete portions. Forexample, the first patterning process may be performed to etch thediaphragm layer 100 to form a first portion 100A coupled to theconnecting structure 86A discretely from a second portion 100B. In someembodiments, the diaphragm layer 100 can be made of polysilicon. Then, asecond interlayer dielectric layer 70C is formed over the diaphragmlayer 100. As an example, the first interlayer dielectric layer 70B maybe a silicon oxide layer. The first interlayer dielectric layer 70B mayhave a thickness in a range of from about 1 μm to about 3 μm. The secondinterlayer dielectric layer 70C may be a silicon oxide layer. The secondinterlayer dielectric layer 70C may have a thickness in a range of fromabout 0.05 μm to about 1 μm.

As shown in a cross-sectional view in FIG. 7, a masking layer 102 isformed over the second interlayer dielectric layer 70C and an opening104 is formed according to the masking layer 102. In some embodiments,the masking layer can include photoresist or a nitride (e.g., Si₃N₄)patterned using a photolithography process. The opening 104 may beformed by a first etching process. In some embodiments, an etchant usedby the first etching process can include a dry etchant having an etchingchemistry comprising a fluorine species (e.g., CF₄, CHF₃, C₄F₈, etc.).In some embodiments, the etchant can include a wet etchant, such as,hydrofluoric acid (HF), Buffered Oxide Etch (BOE) solution, orTetramethylammonium hydroxide (TMAH). The opening 104 may be formedthrough the second interlayer dielectric layer 70C and the diaphragmlayer 100 and reaching into an upper portion of the first interlayerdielectric layer 70B. A depth of the opening 104 is controlled by thefirst etching process to decide a height of a sidewall stopper to beformed in some subsequent process steps. As an example, the upperportion of the first interlayer dielectric layer 70B may have a heightin a range of from about 0.05 μm to about 1 μm. A remaining depth of thefirst interlayer dielectric layer 70B below the opening 104 may be in arange of from about 0.5 μm to about 2.95 μm.

As shown in a cross-sectional view in FIG. 8, a second etching processis performed to the second interlayer dielectric layer 70C to form afirst recess 106 above the diaphragm 50 and to expose a portion of a topsurface of the diaphragm 50. The second etching process is alsoperformed to the first interlayer dielectric layer 70B to form a secondrecess 108 below the diaphragm 50 and to expose a portion of a bottomsurface of the diaphragm 50. The second etching process may be performedwith the masking layer 102 in place. The second etching processcomprises a wet etch that is selective to the first interlayerdielectric layer 70B and the second interlayer dielectric layer 70Crelative to the diaphragm 50, more specifically, the wet etch has anetching rate to the first interlayer dielectric layer 70B and the secondinterlayer dielectric layer 70C at least 20 times greater than anetching rate to the diaphragm 50. Lateral dimensions of the first recess106 and the second recess 108 are controlled by the second etchingprocess to decide a thickness (i.e., a lateral dimension) of thesidewall stopper to be formed in some subsequent process steps. As anexample, the lateral dimensions of the first recess 106 and the secondrecess 108 may be in a range of from about 0.05 μm to about 1 μm.

As shown in a cross-sectional view in FIG. 9, a conformal dielectriclayer 105 is formed on the second interlayer dielectric layer 70C andextended downwardly to sidewalls of the second interlayer dielectriclayer 70C, the diaphragm 50, and the upper portion of the firstinterlayer dielectric layer 70B and the laterally to an upper surface ofthe first interlayer dielectric layer 70B. The conformal dielectriclayer 105 may be formed by a suitable deposition technique such as a PVDprocess or a CVD process. The conformal dielectric layer 105 may be asilicon nitride layer. The conformal dielectric layer 105 may have athickness in a range of from about 0.1 μm to about 2 μm.

As shown in a cross-sectional view in FIG. 10, an a third etchingprocess is performed to the conformal dielectric layer 105 (shown inFIG. 9) to form the sidewall stopper 85 alongside the sidewalls of thesecond interlayer dielectric layer 70C, the diaphragm 50, and the upperportion of the first interlayer dielectric layer 70B. The third etchingprocess is an anisotropical etching process, such as a vertical etchthat removes lateral portions and to leaves vertical portions of theconformal dielectric layer within the recesses 106, 108 of the firstinterlayer dielectric layer and the second interlayer dielectric layer(shown in FIG. 8) and alongside the sidewall of the diaphragm 50. Insome embodiments, an etchant used by the third etching process caninclude a dry etchant having an etching chemistry comprising a fluorinespecies (e.g., CF4, CHF3, C4F8, etc.).

As shown in a cross-sectional view in FIG. 11, an upper dielectric layer70D is formed over the second interlayer dielectric layer 70C and thesidewall stopper 85. A second backplate 60 is formed over the upperdielectric layer 70D. The second backplate 60 may be made of the same ordifferent material than the first backplate 30. In some embodiments, thesecond backplate 60 may be formed by depositing a conformal conductivelayer or a plurality of layers including a conductive layer such as alayer of silicon nitride 60A, a layer of poly-silicon 60B, and anotherlayer of silicon nitride 60C followed by a patterning process. Each ofthese layers can be formed with PVD, CVD, or any other suitabletechniques.

As shown in a cross-sectional view in FIG. 12, a plurality of contacts82, 84, 86, 88 are formed over the upper dielectric layer 70D. Thecontacts may be formed by depositing a contact layer is followed by apatterning process. Examples of the materials for forming the contactsinclude silver, gold, copper, aluminum, aluminum-copper alloy,gold-copper alloy or other suitable conductive materials. The lowerdielectric layer 70A, the first interlayer dielectric layer 70B, and thesecond interlayer dielectric layer 70C, and the upper dielectric layer70D collectively form an interlayer dielectric layer (see an interlayerdielectric layer 70 shown in FIG. 2, FIG. 3, or FIG. 15) that provideelectrical isolation and mechanical supports for various components onthe substrate 40.

As shown in a cross-sectional view in FIG. 13, a first protection layer72 is formed and patterned to form a first opening 75 through the firstprotection layer 72 and overlying the diaphragm 50. A second protectionlayer 42 is deposited on the substrate 40. Example protection layers forthe first protection layer 72 and the second protection layer 42 includea photoresists layer or a dielectric material layer (e.g., siliconnitride). Some areas of the second protection layer 42 are removed toform a protection mask on the substrate 40 that opens up selected partsof the substrate 40 for an etching process. The substrate 40 ispatterned to form a second opening 45 through the substrate 40 at aposition corresponding to the diaphragm 50. In some embodiments, theopening 45 on the substrate 40 can be opened up by anisotropic plasmaetching.

As shown in a cross-sectional view in FIG. 14, an etch is performed torelease the diaphragm 50 to be movable relative to the first backplate30 and the second backplate 60. The interlayer dielectric layer 70 isetched with a wet etchant, starting from both the opening 45 on thesubstrate 40 and the opening 75 on the interlayer dielectric layer 70,to form the diaphragm 50 and possibly the suspended backplate 60.Examples of the wet etchant that can be used for etching the interlayerdielectric layer 70 include hydrofluoric acid (HF), Buffered Oxide Etch(BOE) solution (6 parts 40% NH₄F and 1 part 49% HF), orTetramethylammonium hydroxide (TMAH)). Thus the diaphragm 50 isconfigured to deflect under an air pressure when the air pressure islarger or smaller than a predetermined value. The sidewall stopper 85 isconfigured to protect the diaphragm 50 from stick to the first backplate30 and/or the second backplate 60.

As shown in a cross-sectional view in FIG. 15, both the first protectionlayer 72 and the second protection layer 42 are removed. Theseprotection layers can be stripped off with chemicals or etched away withetchant. After removing these protection layers, the MEMS microphone 95having the diaphragm 50 with a sidewall stopper 85 is fabricated. TheMEMS microphone 95 as fabricated includes an electrical contact 82electrically connected to the backplate 60 that forms a first terminalfor the capacitive element, and an electrical contact 84 electricallyconnected to the diaphragm 50 that forms a second terminal for thecapacitive element. In addition, the MEMS microphone 95 can include oneor more contacts (e.g., a contact 86, the only one shown in the figure)that connect to pre-fabricated CMOS circuits (not shown in the figure)on the substrate through via holes. The pre-fabricated CMOS circuits canprovide the electronics for supporting the operation of the MEMSmicrophone 95. In some embodiments, the pre-fabricated CMOS circuits canbe fabricated, using suitable process, on the substrate 40 before thelower dielectric layer 70A is formed on the substrate 40 (as shown inFIG. 4).

FIG. 16 illustrates a flow diagram of a method for manufacturing a MEMSdevice in accordance with some embodiments. The MEMS device includes asidewall stopper clamped on edges of openings of a movable diaphragm toprovide stiction protection to the movable diaphragm. Examples of theMEMS device are shown in FIGS. 4-15. Although FIGS. 4-15 are describedin relation to the method shown in FIG. 16, it will be appreciated thatthe structures disclosed in FIGS. 4-15 are not limited to the methodshown in FIG. 16, but instead may stand alone as structures independentof the method shown in FIG. 16. Similarly, although the method shown inFIG. 16 is described in relation to FIGS. 4-15, it will be appreciatedthat the method shown in FIG. 16 is not limited to the structuresdisclosed in FIGS. 4-15, but instead may stand alone independent of thestructures disclosed in FIGS. 4-15. Also, while disclosed methods (e.g.,the method shown in FIG. 16) are illustrated and described below as aseries of acts or events, it will be appreciated that the illustratedordering of such acts or events are not to be interpreted in a limitingsense. For example, some acts may occur in different orders and/orconcurrently with other acts or events apart from those illustratedand/or described herein. In addition, not all illustrated acts may berequired to implement one or more aspects or embodiments of thedescription herein. Further, one or more of the acts depicted herein maybe carried out in one or more separate acts and/or phases.

At act 1602, a semiconductor substrate is provided and a diaphragm layeris formed between first interlayer dielectric layer and secondinterlayer dielectric layer. See, for example, as shown by across-sectional view shown in FIG. 6.

At act 1604, a first etch is performed to the first interlayerdielectric layer, the diaphragm and the second interlayer dielectriclayer to form an opening. See, for example, as shown by across-sectional view shown in FIG. 7.

At act 1606, a second etch is performed to extend the opening in lateraland form recesses above and below the diaphragm. See, for example, asshown by a cross-sectional view shown in FIG. 8.

At act 1608, a sidewall stopper is formed along a sidewall of thediaphragm. See, for example, as shown by a cross-sectional view shown inFIGS. 9-10.

At act 1610, a protection layer is formed and patterned to form a firstopening through the protection layer. The substrate is patterned to forma second opening through the substrate at positions corresponding to thediaphragm. See, for example, as shown by a cross-sectional view shown inFIG. 13.

At act 1612, an etch is performed to release the diaphragm. See, forexample, as shown by a cross-sectional view shown in FIG. 14.

Thus, as can be appreciated from above, the present disclosure relatesto a MEMS device and associated methods. Though the above descriptionuses a MEMS microphone as an example, the disclosed sidewall stopper canbe implemented in varies MEMS devices. In those devices, the sidewallstopper is clamped to edges of an opening (a venting hole or otheropening structures) partially or throughly disposed within a movablediaphragm of a MEMS device). The sidewall stopper is used to protect themovable diaphragm from stiction. The sidewall stopper locates alongsidea sidewall of the opening and may vertically extend above and/or belowthe movable diaphragm and laterally extend across an edge of the openingof the diaphragm.

In some embodiments, the present disclosure relates a microphone. Themicrophone includes a substrate having an opening disposed through thesubstrate. A diaphragm is disposed over the substrate and facing theopening of the substrate. The diaphragm has a venting hole overlying theopening of the substrate. A backplate is disposed over and spaced apartfrom the diaphragm. A sidewall stopper is disposed along a sidewall ofthe venting hole of the diaphragm.

In other embodiments, the present disclosure relates to a MEMS device.The MEMS device includes a substrate having an opening disposed throughthe substrate. A first backplate is disposed over the substrate andfacing the opening of the substrate. A second backplate is disposed overthe first backplate. A diaphragm locates between the first backplate andthe second backplate and includes an opening disposed therethrough. Thediaphragm is spaced apart from the first backplate by a first distanceand spaced apart from the second backplate by a second distance. Asidewall stopper is disposed along sidewalls of the opening of thediaphragm.

In yet other embodiments, the present disclosure relates to a method ofmanufacturing a MEMS device. In the method, a first interlayerdielectric layer is formed over a substrate, and a diaphragm is formedover the first interlayer dielectric layer. Then, a second interlayerdielectric layer is formed over the diaphragm. A first etch is performedto form an opening through the second interlayer dielectric layer andthe diaphragm and reaching into an upper portion of the first interlayerdielectric layer. A second etch is performed to the first interlayerdielectric layer and the second interlayer dielectric layer to formrecesses above and below the diaphragm and to respectively expose aportion of a top surface and a portion of a bottom surface of thediaphragm. A sidewall stopper is formed along a sidewall of thediaphragm into the recesses of the first interlayer dielectric layer andthe second interlayer dielectric layer

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A microphone comprising: a substrate having anopening disposed through the substrate; a diaphragm disposed over thesubstrate and facing the opening of the substrate, the diaphragm havinga venting hole overlying the opening of the substrate; a backplatedisposed over and spaced apart from the diaphragm; and a sidewallstopper disposed along a sidewall of the venting hole of the diaphragm.2. The microphone of claim 1, wherein the sidewall stopper has an upperportion higher than a top surface of the diaphragm and a lower portionlower than a bottom surface of the diaphragm.
 3. The microphone of claim1, wherein the sidewall stopper laterally extends across an edge of theventing hole and includes an upper portion contacting a top surface ofthe diaphragm and a lower portion contacting a bottom surface of thediaphragm; wherein the upper portion and the lower portion of thesidewall stopper clamp the diaphragm therebetween.
 4. The microphone ofclaim 1, wherein the sidewall stopper comprises silicon nitride.
 5. Themicrophone of claim 1, wherein the sidewall stopper comprisespolysilicon.
 6. The microphone of claim 1, wherein a height of thesidewall stopper is greater than a distance between the backplate andthe diaphragm when the diaphragm is in a relax position.
 7. Themicrophone of claim 1, wherein the backplate comprises a first siliconnitride layer, a second silicon nitride layer and a polysilicon layerdisposed between the first silicon nitride layer and the second siliconnitride layer.
 8. A MEMS device, comprising: a substrate having anopening disposed through the substrate; a first backplate disposed overthe substrate and facing the opening of the substrate; a secondbackplate disposed over the first backplate; a diaphragm located betweenthe first backplate and the second backplate and including an openingdisposed therethrough, wherein the diaphragm is spaced apart from thefirst backplate by a first distance and spaced apart from the secondbackplate by a second distance; and a sidewall stopper disposed alongsidewalls of the opening of the diaphragm.
 9. The MEMS device of claim8, wherein the sidewall stopper extends in a vertical direction upwardlyto a first position between the first backplate and the diaphragm anddownwardly to a second position between the diaphragm and the secondbackplate.
 10. The MEMS device of claim 8, wherein the sidewall stopperhas a ring shape that continuously extends along a perimeter of theopening of the diaphragm.
 11. The MEMS device of claim 8, wherein thefirst backplate and the second backplate respectively comprises a firstsilicon nitride layer, a second silicon nitride layer and a polysiliconlayer disposed between the first silicon nitride layer and the secondsilicon nitride layer.
 12. The MEMS device of claim 8, wherein thesidewall stopper laterally extends across a boundary edge of the openingof the diaphragm.
 13. A MEMS device, comprising: a first interlayerdielectric layer disposed over a substrate; a diaphragm disposed overthe first interlayer dielectric layer; a second interlayer dielectriclayer disposed over the diaphragm; and a sidewall stopper disposed alonga first sidewall of the diaphragm, wherein the sidewall stopper extendsinto recesses of the first interlayer dielectric layer and the secondinterlayer dielectric layer above and below the diaphragm.
 14. The MEMSdevice of claim 13, wherein the diaphragm has a second sidewall and aportion of a top surface directly contacting the second interlayerdielectric layer.
 15. The MEMS device of claim 13, wherein the diaphragmhas a portion of a bottom surface directly contacting the firstinterlayer dielectric layer.
 16. The MEMS device of claim 13, whereinthe diaphragm is made of silicon nitride or polysilicon.
 17. The MEMSdevice of claim 13, wherein the sidewall stopper is made of siliconnitride or polysilicon.
 18. The MEMS device of claim 13, furthercomprising a first backplate disposed between the first interlayerdielectric layer and the substrate.
 19. The MEMS device of claim 13,further comprising a second backplate disposed over the secondinterlayer dielectric layer and the sidewall stopper.
 20. The MEMSdevice of claim 13, further comprising: a first opening overlying thediaphragm and disposed through a protection layer; and a second openingdisposed directly under the diaphragm through the substrate.